Method of making a cryogenic tank



Oct. 7, 1969 v. N. TRAMONTINI METHOD OF MAKING A CRYOGENIC TANK 2Sheets-Sheet 1 Filed Sept. 2?, i966 United States Patent 3,470,606METHOD OF MAKING A CRYOGENIC TANK Vernon N. Tramontini, Indianapolis,Ind., assignor to Stewart-Warner Corporation, Chicago, 111., acorporation of Virginia Filed Sept. 27, 1966, Ser. No. 582,308 Int. Cl.B23k 1/04; 1323 21/60 US. Cl. 29-469 8 Claims ABSTRACT OF THE DISCLOSUREThe present invention relates to a cryogenic tank adapted to be usedwith a truck, railway car or the like for transporting a refrigeratedliquified gas such as nitrogen, and to a method of making such a tank.

Liquified gases are frequently stored and transported in cryogenic tanksor Dewars. In the case of liquified nitrogen, the tank must necessarilywithstand an internal pressure of about 200 p.s.i., taking intoconsideration the maximum pressure of the liquid therein during fillingand allowing a suitable safety factor. The most common type of cryogenictank now in use is comprised of a plurality of generally U-shaped platesarranged in series and welded together to form a rectangular tank. Thetransverse portions of the plates, which are spaced about 8 inchesapart, strengthen the tank against burst and prevent sloshing of theliquid therein. This tank, in turn, is supported within an outerhousing, and a vacuum is maintained, and insulation provided, in thespace between the tank and the housing. This arrangement has provedunsatisfactory because of the extensive number and length of exposedweld seams in the tank. When the slightest crack develops along anyseam, the surrounding vacuum is lost and the liquid in the tank soonboils off because of the excessive heat leak.

It is an object of the present invention to provide a cryogenic tank,and a method of making the same, wherein the number and length ofexternal weld seams is maintained at a minimum.

It is another object of the present invention to provide a cryogenictank, and a method of making the same, wherein substantially all of theparts thereof are joined together in a brazing operation.

It is another object of the present invention to provide a cryogenictank, and a method of making the same, comprised of side walls and aplurality of corrugated bafiie plates so arranged therebetween that thestrength of the corrugations may be utilized during assembly withoutaffecting reinforcement by the baffie plates of the side walls in thefinal assembly.

It is a further object of the present invention to provide a cryogenictank, and a method of making the same, wherein strips of brazing foilare folded over the edges of the battle plates prior to arranging thembetween the side walls in order to accomplish the brazing.

Now, in order to acquaint those skilled in the art with the manner ofthe constructing and using cryogenic tanks in accordance with theprinciples of the present invention,

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there will be described in connection with the accompanying drawings apreferred embodiment of the invention.

In the drawings:

FIGURE 1 is a perspective view of a cryogenic tank embodying theprinciples of the present invention;

FIGURE 2 is a sectional view, on an enlarged scale and with certainportions being broken away, taken substantially along the line 22 inFIGURE 1,. looking in the direction indicated by the arrows;

FIGURE 3 is a fragmentary sectional view, on a further enlarged scale,taken substantially along the line 33 in FIGURE 2, looking in thedirection indicated by the arrows;

FIGURE 4 is a view, partly in section and partly in elevation and on aslightly reduced scale, taken substantially along the line 4-4 in FIGURE2, looking in the direction indicated by the arrows;

FIGURE 5 is a fragmentary sectional view illustrating a portion of atank module in a pre-assembly stage; and

FIGURE 6 is a fragmentary and elevational view of the portion of thetank module of FIGURE 5.

Referring now to FIGURE 1, there is indicated generally by the referencenumeral 10 a rectangular cryogenic tank constructed in accordance withthe principles of the present invention. The tank 10 is preferablycomposed of two modules or sections 12 and 14 which, as will bepresently explained, are first fabricated individually and then joinedtogether.

As shown in FIGURES 1-4, the module 12 is comprised of a pair of flatrectangular parallel side panels 16 and 18 presenting peripheral edges,a plurality of baffle plates or fins 20 extending between the panels,and formed end wall portions 22, 24 and 26 extending between and alongthree edges of the panels whereby the module presents one open end. Tobe noted is that the baffle plates 20 are each formed with a pluralityof parallel corrugations that are arranged to extend perpendicular tothe side panels 16 and 18. In addition, angle bars 28 and 30 aredisposed along the edges of the side panels 16 and 18 adjacent the openend of the module 12, and pairs of angle strips 32 are locatedlengthwise of the end wall portions 22, 24 and 26.

Although the module 12 is used in an upright position with the sidepanels 16 and 18 extending vertically, during fabrication the module islaid on its side with the side panels disposed horizontally as shown inFIGURES 5 and 6. In the assembly operation, strips of brazing foil 34are folded over the side edges of the baffle plates 20 and the latterare arranged between the side panels 16 and 18 with the brazing foil incontact with the panels. The bafile plates 20 are maintained in spacedrelation by means of lateral locating tabs 36 punched therefrom atstaggered locations in alternative plates. Also, the end wall portions22, 24 and 26, the angle bars 28 and 30, and the angle strips 32 arelocated in the relative positions shown in FIGURES 1-4, and suitablebrazing foil or wire is disposed along the edges of the foregoing parts.The abutting edges of the end wall portions 22 and 24, and 24 and 26,are preferably welded together, and tack Welding may be performed atspaced locations to maintain the side panels, end wall portions, anglebars and angle strips in proper position prior to brazing.

Preparatory to the brazing operation and while the lower side panel 16(FIGURES 5 and 6) is supported on a platform 38, a weighted member orgating 40 is placed on the upper side panel 18 whereby compressiveforces are applied to the outer faces of the side panels 16 and 18. Thedescribed assembly is then immersed in a fluxing salt bath in a furnace,and the brazing foil is heated to proper brazing temperature. Finally,the assembly is removed from the salt bath, air cooled rapidly for heattreating and water quenched to aid in salt removal. During the brazingoperation, the sides edges of the bafile plates 20 are joined to theinner faces of the side panels 16 and 18, and the other parts of themodule 12 are similary joined together. If desired, the end wallportions 22, 24 and 26 may :be joined to the side panels 16 and 18 bywelding rather than brazing.

The module 14 is assembled and fabricated in a brazing operation in thesame manner as the module 12. Therefore, a detailed description thereofis deemed unnecessary. Like reference numerals followed by the subscriptletter a have been used to indicate those parts of the module 14 thatare the same as or similar to the parts of the module 12.

In the final stages of tank assembly, brackets 42 and 44 (FIGURES 2 and3) are tack welded to the angle bar 30 of the module 12, a filler tube46 is tack welded to the brackets 42 and 44, and a locating plate 48 istack welded to the tiller tube 46. Then, the modules 12 and 14 at theiropen ends are secured together as by welding to form the closed tank 10.The side panels 16-1611 and 18-18a define the tank side walls, while theend wall portions 22-22a, 24, 24a, and 2626a define the tank end walls.To complete the tank 10, a bellows filler neck 50 is disposed throughthe end wall portions 22 and 22a at the junction thereof and is suitablysecured in position as by welding. As will be appreciated from theforegoing description, the number and length of external weld seams ismaintained at a minimum, thereby reducing the risk of leaks andimproving the service life of the tank.

In the above-described tank construction, the corrugations of the bafileplates 20 extend perpendicular to the side Walls of the tank. Thisarrangement of the corrugations offers complementary advantages. On theone hand, the corrugations serve to rigidify the baffie plates so thatthe latter will withstand the compressive forces applied during thebrazing operation when the modules are laid on their sides. On the otherhand, they do not interfere with reinforcement by the baffle plates onthe side walls when the tank is filled with liquid under pressure.Contrastingly, if the corrugations were arranged parallel to the sidewalls, they would not reinforce the side walls; the walls would bulgeout under internal pressure and the corrugations would thereby bestraightened as in an accordion being extended. In the presentconstruction, the rigidifying qualities of the corrugations are utilizedduring assembly, and yet the corrugations are oriented so as to preventany accordion effect in the final assembly. The baffle plates also servein a conventional manner to prevent sloshing of liquid within the tank.

Additionally, the use of strips of brazing foil folded over the edges ofthe bafile plates simplifies the preparation for brazing and effectsmore uniform brazing that contributes to improved tank strength.Finally, the angle bars 28 and 28a and 30 and 30a serve to retain thebaflle plates 20 in position during the brazing operation, the anglebars 28 and 28a back up the abutting edges of the side panels duringwelding of the modules 12 and 14 together, and the angle bars addstructural strength to the center portion of the tank where there are nobafile plates.

For storage of liquid nitrogen, and consistent with safety, a tankshould withstand an internal pressure up to 200 psi. A 400-gallon tankof the present invention that satisfactorily mets this requirement hasthe following general specifications. The tank has a height of about 76inches, a width of about 80 inches and a depth of about 18 inches; thevarious parts of the tank are made of 6061 aluminum; the side panels,formed end wall portions and angle bars and strips have a thickness of.125 inch, the baffle plates a thickness of .020 inch, and the brazefoil a thickness of .003 inch; and the baflle plates are spaced 1 /2inches apart with the amplitude of the corrugations being At-inch andthe wave length 6 inches. The foregoing general specifications are givenfor illustrative purposes only. It should be appreciated that theoverall dimensions may be varied to provide tanks of modified externalconfiguration or of smaller or larger capacity, and that the otherspecifications may be varied relatively to accommodate the same, orlower or higher, internal pressures. The tank 10 is preferablypreassembled in two sections because of size and also to permit thefiller tube 46 to be centrally located as disclosed herein. Finally, thetank 10 is normally mounted in a thermally insulated outer housing.However, such a housing has not been shown or described in detailbecause it does not form part of the present invention.

While there has been shown and described a preferred embodiment of thepresent invention, it will be understood by those skilled in the artthat various rearrangements and modifications may be made thereinwithout departing from the spirit and scope of the invention.

I claim:

1. A method of fabricating a cryogenic tank composed of two modules eachcomprised of flat rectangular parallel side panels and end wall portionsand a plurality of bafile plates each formed with a plurality ofparallel corrugations, comprising first fabricating each module by thesteps of arranging the battle plates in spaced relationship with oneanother between the side panels with the corrugations of the bafileplates disposed perpendicular to the side panels, disposing the end wallportions between and along the edges of the side panels whereby eachmodule presents one open end, applying a compressive force to the sidepanels while the bafile plates are maintained rigid by the corrugationsthereof, joining the end wall portions and the bathe plates to the sidepanels in a brazing operation; and then securing the two modulestogether at their open ends toprovide a closed tank.

2. The method of claim. 1 wherein the side panels are disposedhorizontally during the brazing operation and the compressive forces areapplied by placing a weighted member on the module.

3. In the method of claim 1 in which the bafile plates are arranged inspaced relationship with one another with the aid of lateral locatingtabs punched in each of the baffle plates.

4. In the method of claim 2 in which the baffie plates are arranged inspaced relationship with one another with the aid of lateral locatingtabs punched in each of the bathe plates.

5. In a method of fabricating a liquid storage cryogenic tank of flatrectangular parallel side panels, end wall portions and a plurality ofbafile plates each formed with a plurality of parallel corrugations,comprising the steps of arranging the baffle plates in spacedrelationship with one another between the side panels with thecorrugations of the baffle plates disposed perpendicular to the sidepanels, disposing the end wall portions between and along the edges ofthe side panels, applying a compressive force to the side panels whilethe baffle plates are maintained rigid by the corrugations thereof, andjoining the end wall portions and the baffle plates to the side panelsin a brazing operation.

6. The method of claim 5 wherein the side panels are disposedhorizontally during the brazing operation and the compressive forces areapplied by placing a weighted member on the module.

7. In the method of claim 5 in which the bafile plates are arranged inspaced relationship with one another with the aid of lateral locatingtabs punched in each of the bafiie plates.

8. In the method of claim 6 in which the bafile plates are arranged inspaced relationship with one another 5 6 with the aid of laterallocating tabs punched in each of the 3,072,225 1/ 1963 Crerner. baffieplates. 3,168,782 2/1965 Cochran.

References Cited JOHN F. CAMPBELL, Primary Examiner UNITED STATESPATENTS 5 J. L. CLINE, Assistant Examiner 2,900,713 8/1959 Young.

US .Cl. X.R. 2,982,441 5/1961 Farrell 220 71 29 4711, 501 3,024,9383/1962 Watter 29-469 X

